Most conventional DC power supply circuits reduce voltage by using transformers. The power supply circuit of the invention, in contrast, uses a capacitor as the voltage reducing component and a bridge type current rectifier device for converting AC current to DC current resulting in a power supply having a smaller volume, lower weight, and lower cost.
While high frequency carrier wave controlled switching type power supply circuits have a similar volume and weight, capacitor abased circuits have less heat loss and lower cost than such switching type power supplies, and in addition eliminate noise interference (EMC). Therefore, application of this type of power supply has gradually expanded from low power applications to medium and large power applications.
Because the effect of using a capacitor as a voltage reducing component is essentially the same as using the conventional series-combined resistors, i.e., the output terminal voltage is inversely related to the output current, control of the capacitor-based power supply circuit is as follows: when the output current is increased, the output terminal voltage is reduced, while when the output current is decreased, the output terminal voltage will be raised. In addition, the capacitor regulated circuit can be further installed with a controllable current distributing circuit device parallel connected with the output terminals of the current rectifier device to actively control the output voltage.
It is thus an objective of the invention to provide an improved voltage and current power supply circuit made up of a voltage reducing and current limiting rectifying circuit formed by capacitors and a bridge type current rectifier device. The output terminals of the rectifying circuit are parallel connected to a current distributing circuit device which controls the output voltage.